The present invention relates generally to oscillators and more particularly to coupled oscillators.
Oscillator phase noise can be improved by coupling multiple (e.g., N) oscillators together. This improvement can be intuitively understood as distributing the noise in each oscillator over N-coupled modes instead of a single mode of oscillation and confining the oscillation signal in the selected mode, which implies the improvement in signal-to-noise ratio by a factor of 10 log N. Another intuitive way to explain such signal-to-noise improvement is as follows. By distributing (and thereby summing) the uncorrelated noise from multiple sources (i.e., oscillators) into each mode, some of the noise is statistically cancelled (due to noise of opposite polarities) resulting in an improvement (e.g., 10 log N) in oscillator phase noise. However, adding oscillators and coupling them to each other in a conventional manner may increase the required circuit area by a factor of N or more.